warn_unreachable false positive when reassigning in loop

[Garrett-R]

Bug Report

To Reproduce

-Run this code with warn_unreachable enabled:

x: int|None = None
x = None
for _ in range(2):
    if x is None:
        print('None')
        x = 2
    else:
        print('Not None')

(Mypy playground)

Expected Behavior

No errors.

Actual Behavior

main.py:8: error: Statement is unreachable  [unreachable]

(this is wrong, the script indeed hits line 8 and prints Not None)

Your Environment

• Mypy version used: 1.5.1
• Mypy configuration options from mypy.ini (and other config files): warn_unreachable = true
• Python version used: 3.11.4

[erictraut]

I think this may be a duplicate of #14987, #11612, #10634, #8865, and #8721. All of these seem to be manifestations of the same underlying bug.

[Garrett-R]

Ah yes, you're right, my bad! I had tried searching before creating this, but somehow missed all those. Closing.